class Gem::ConflictError

def initialize(target, conflicts)
  @target    = target
  @conflicts = conflicts
  @name      = target.name
  reason = conflicts.map do |act, dependencies|
    "#{act.full_name} conflicts with #{dependencies.join(", ")}"
  end.join ", "
  # TODO: improve message by saying who activated `con`
  super("Unable to activate #{target.full_name}, because #{reason}")
end